Battery cell having repair reservoir

Abstract

The invention relates to a battery cell comprising: a housing (2), a cell stack (3) having an electrode, in particular an anode (31), a liquid electrolyte, wherein the cell stack (3) and the electrolyte are arranged in the housing (2), and a reservoir (5) having a repair substance which is designed to form a boundary layer on the electrode, wherein the reservoir (5) is arranged in the housing (2), and wherein the reservoir (5) is designed to dispense the repair substance to the electrolyte in order to repair damage at the boundary layer.

Description

[0001] November 17, 2025 Mattausch

[0002] Applicant: Carl Freudenberg KG, 69469 Weinheim

[0003] Battery cell with healing reservoir

[0004] Description

[0005] The present invention relates to a rechargeable battery cell, in particular a lithium-ion battery cell, with a reservoir containing a healing substance, which can significantly extend the service life of the battery cell.

[0006] Recently, there have been increasing attempts to enhance the storage capacity of lithium-ion battery cell anodes, which are typically graphite-based, by doping them with silicon or silicon dioxide. This allows for more lithium to be stored in the anode. However, a practical problem is the significant risk that these silicon-based particles will undergo considerable volumetric expansion during cell cycling. Charged silicon particles can expand by up to 300% compared to discharged particles. This volume expansion can lead to localized damage to the solid electrolyte interphase (SEI), which protects the electrolyte from oxidative degradation.

[0007] It is therefore known that substances added in small quantities to a liquid electrolyte in its initial state form a boundary layer (passivation layer) at the anode when a voltage is first applied to the battery cell (the so-called formation). This boundary layer is also called the solid electrolyte interphase (SEI). The SEI ensures that the electrolyte is not in direct contact with the anode surface and cannot be oxidized. The presence of an intact SEI is essential for a long battery lifespan.

[0008] If the boundary layer breaks down during operation, decomposition reactions of the electrolyte occur, which over time reduce the electrical capacity of the battery cell, increase the internal pressure of the battery cell and thus determine the lifespan of the battery cell over time.

[0009] It is therefore an object of the present invention to provide a battery cell that has an extended service life while being easy and inexpensive to manufacture. This object is achieved by a battery cell with the features of claim 1. The dependent claims describe preferred embodiments of the invention.

[0010] The rechargeable battery cell according to the invention, with the features of claim 1, has the advantage that a boundary layer at one electrode, in particular the anode, can be maintained throughout the entire service life of the battery cell. This prevents decomposition reactions of the electrolyte. According to the invention, if damage to the boundary layer at the electrode occurs, the boundary layer can be repaired during operation of the cell. This makes it possible, in particular, for a substance that forms the boundary layer at the beginning of the battery cell's use and that is mixed into the electrolyte to constitute only a small proportion of the electrolyte, in particular less than 0.5 vol%. This allows for an optimized electrolyte composition.

[0011] According to the invention, this is achieved by the battery cell comprising a housing, a cell stack or cell winding (hereinafter referred to simply as "cell stack" for the sake of simplicity) with electrodes, in particular an anode and a cathode, and a liquid electrolyte. The cell stack and the electrolyte are arranged within the housing. Furthermore, the battery cell includes a reservoir containing a healing substance or a plurality of healing substances (hereinafter referred to simply as "healing substance"), which is configured to repair a damaged boundary layer at an electrode, in particular the anode. The reservoir containing the healing substance is arranged within the housing and is configured to release the healing substance into the electrolyte. Thus, the battery cell has the capability to repair a damaged boundary layer by using the healing substance from the reservoir to repair the damage to the boundary layer.

[0012] Furthermore, it is preferably ensured that the concentration of the healing substance in the battery cell is kept so low throughout its entire lifespan, in particular less than or equal to 0.5 vol-% of the electrolyte, that no adverse properties occur in the function of the electrolyte.

[0013] The battery cell reservoir is preferably pressure-activated, so that the healing substance is released into the electrolyte when pressure is applied to the reservoir. This pressure is preferably generated by increasing the internal pressure within the battery cell. The pressure-activated reservoir has the advantage that pressure typically increases inside the battery cell during operation. Thus, over time, a continuously increasing pressure is exerted on the reservoir. Since the rising internal cell pressure can be caused, among other things, by electrolyte depletion, a healing mechanism can be triggered directly and automatically by pressure activation. The reservoir is designed such that it releases the healing substance into the electrolyte depending on the pressure.

[0014] Preferably, the pressure-activated reservoir is designed such that the amount of therapeutic substance released increases with increasing pressure. Since the pressure inside the battery cell tends to increase towards the end of its lifespan and the number of charging cycles, the amount of therapeutic substance released from the reservoir also increases in proportion to the battery cell's lifespan.

[0015] Preferably, the reservoir is thermally activatable. This allows the release of the therapeutic substance into the electrolyte as the battery cell temperature rises. Thermal activation of the reservoir can be the sole activation method or combined with pressure activation. The reservoir is preferably designed such that the release of therapeutic substance into the electrolyte begins when a temperature threshold is reached in the reservoir's surrounding area. Furthermore, the higher the temperature rises in the reservoir's vicinity, the greater the amount of therapeutic substance released.

[0016] In this case, the reservoir is particularly preferably arranged in the battery cell in a position where a maximum temperature is reached in the battery cell during operation.

[0017] Furthermore, the healing substance is preferably the same substance as the substance contained in the electrolyte for the formation of the boundary layer at the electrode at the beginning of the battery cell's use.

[0018] Preferably, the therapeutic substance is contained within a capsule with a breakable capsule shell. By selecting a specific wall thickness for the capsule shell and / or incorporating defined mechanical weak points, a precise moment for opening the capsule shell and releasing the therapeutic substance can be chosen. Furthermore, a melting zone within the capsule material can preferably be designed to allow thermal activation. Different capsule sizes and capsules with different shell materials are also conceivable, enabling two- or multi-stage initiation of the therapeutic substance release. Preferably, the capsule can also be activated externally, either mechanically, for example, by applying vibrations to the capsule, and / or thermally by external heating.

[0019] The reservoir is preferably planar and integrated into a component of the battery cell or loosely arranged within the battery cell. According to a further preferred embodiment of the invention, the battery cell comprises a sponge impregnated with the therapeutic substance.

[0020] Preferably, the battery cell has a non-woven fabric soaked with the healing substance.

[0021] Furthermore, the battery cell preferably has a fiber ball soaked with the healing substance.

[0022] Preferably, the battery cell comprises a healing substance which is adsorbed in a porous material, in particular activated carbon and silica gel.

[0023] Preferably, the battery cell comprises a gel containing a therapeutic substance. The gel preferably serves as a carrier medium for the therapeutic substance.

[0024] Furthermore, the battery cell preferably has a polymer with absorbed healing substance.

[0025] Preferably, the battery cell comprises a highly porous inorganic material, in particular activated carbon or silica gel, in whose pores the healing substance is deposited.

[0026] Other possible combinations include, for example, a non-woven fabric as a carrier material with a recess in which a sponge or porous materials impregnated with the healing substance are arranged. Preferably, the healing substance is also arranged within the non-woven fabric.

[0027] According to a particularly preferred embodiment of the invention, the battery cell comprises a cell shell in which the cell stack is arranged. The cell shell is thus arranged between the battery cell housing and the cell stack. The reservoir is preferably arranged on the cell shell. The reservoir can be arranged on the cell shell facing exclusively towards the cell stack and / or be arranged in a recess in the cell shell and / or be arranged on a side of the cell shell facing the housing.

[0028] More preferably, the battery cell comprises a base element, which is particularly arranged at the bottom of the cell casing, and on which the reservoir is arranged. Thus, the reservoir is arranged below the cell stack.

[0029] The battery cell preferably has several reservoirs, which can preferably be activated differently. Particularly preferably, the battery cell has a pressure-activated reservoir and a temperature-activated reservoir. The reservoirs are preferably arranged at different positions within the battery cell.

[0030] The therapeutic substance preferably comprises vinyl carbonate (VC).

[0031] The therapeutic substance preferably comprises fluoroethylene carbonate (FEC). The therapeutic substance further preferably comprises vinyl ethylene carbonate or a substance selected from the group of sultones, in particular 1,3-propane sultone.

[0032] The healing substance is still preferably a mixture of healing individual substances, in particular a mixture of the substances listed above.

[0033] Preferably, the battery cell comprises a first and a second reservoir, which are configured to be activated at different times and / or which are configured to release different amounts of therapeutic substance. This allows for staged activation of the reservoirs when at least two reservoirs are arranged. In particular, this makes it possible to maintain a substantially constant proportion of therapeutic substance in the electrolyte over the battery cell's lifetime, ensuring that sufficient therapeutic substance is always present in the electrolyte throughout the entire lifespan of the battery cell. For example, the activation of the first reservoir can be temperature-dependent and the activation of the second reservoir pressure-dependent.It is also conceivable that one or both reservoirs could be activated from outside the battery cell, for example mechanically by means of vibrations and / or by heating the battery cell from the outside at different times. This could be the sole activation method or an additional method alongside pressure-based and / or temperature-based activation of the reservoirs.

[0034] Preferably, the first activation mechanism of the first reservoir differs from the second activation mechanism of the second reservoir. However, it is also possible for the first and second reservoirs to be activated by the same activation mechanism, for example, pressure, if the arrangement of the two reservoirs in the housing is such that one reservoir is located in a housing area that is stiffer than another area. Since the less stiff area deforms first during operation, this reservoir would be activated first.

[0035] Preferably, the battery cell has a monitoring unit which is configured to detect a deterioration of the electrolyte's condition and then, in particular, to activate at least one reservoir of the battery cell containing healing substance in order to release healing substance from the reservoir.

[0036] Preferably, the reservoir is fixed by means of an adhesive bond. This allows the reservoir to be positioned easily and cost-effectively at any desired location within the battery cell. The battery cell is preferably a prismatic cell, a pouch cell, or a cylindrical cell. The housing is preferably a metallic housing, in particular an aluminum housing, a steel housing, or a foil housing.

[0037] Preferred embodiments of the invention are described in detail below with reference to the accompanying drawing. The drawing shows:

[0038] Figure 1 shows a schematic, perspective view of a battery cell according to a first preferred embodiment of the invention.

[0039] Figure 2 is a schematic, perspective view of a cell shell of the battery cell from Figure 1 in an unfolded state.

[0040] Figure 3 is a diagram showing the concentration K of a substance for the formation of a boundary layer at an electrode over a number of charging cycles.

[0041] Figure 4 shows a schematic, perspective view of a battery cell according to a second embodiment of the invention.

[0042] Figure 5 shows a schematic, perspective view of a cell shell of a battery cell according to a third embodiment of the invention.

[0043] Figures 6 and 7 show schematic sectional views of a battery cell according to a fourth embodiment of the invention with a healing substance capsule.

[0044] A rechargeable battery cell 1 according to a first preferred embodiment of the invention is described in detail below with reference to Figures 1 to 3.

[0045] Figure 1 schematically shows the structure of the battery cell 1 with a metallic housing 2, a cell stack 3 and a cell shell 4. The cell shell 4 surrounds the cell stack 3. The cell stack 3 comprises, as schematically shown in Figure 1, electrodes in the form of an anode 31 and a cathode 32.

[0046] The cell stack 3, arranged in the cell shell 4, is thus located in the metallic housing 2. The metallic housing 2 is filled with an electrolyte (not shown) and has a lid (not shown).

[0047] In its initial state, the electrolyte contains an additional substance designed to form an interface layer at the electrodes, particularly at the anode, upon application of an initial voltage. This interface layer is called the solid electrolyte interphase (SEI). The anode contains graphite and preferably a silicon content of more than 5 vol%. The interface layer is formed when a voltage is first applied to the battery cell 1, a process known as cell formation. The SEI prevents electrolyte decomposition during cell operation.

[0048] In particular, during each charging process of the battery cell, this boundary layer can be attacked or destroyed, at least locally, and electrolyte can be oxidized.

[0049] The substance added to the electrolyte to form the boundary layer at the electrodes cannot be added to the electrolyte in arbitrary quantities. This would significantly impair the performance of the battery cell.

[0050] According to the invention, the battery cell 1 is provided with a reservoir 5 containing a healing substance. The reservoir 5 is arranged in the housing 2 of the battery cell 1 and is configured to release the healing substance into the electrolyte. The healing substance is thus configured to form a boundary layer at the anode or to repair a damaged boundary layer.

[0051] As shown in Figure 2, in the first embodiment a recess 40 is formed in the cell membrane 4. The recess is designed such that the reservoir 5 containing the healing substance can be arranged in the recess 40. This is indicated by the arrow in Figure 2.

[0052] The recess 40 can be a through-recess or a depression in the cell wall, and the reservoir can be fixed to the cell wall 4 in different ways.

[0053] Reference numeral 6 denotes a base element on which the electrodes are arranged and can be supported. The base element 6 is preferably a base fleece.

[0054] Reservoir 5 can be activated by pressure and / or thermally.

[0055] Thus, reservoir 5 can release healing substance into the electrolyte when a pressure threshold and / or a temperature threshold is exceeded. This ensures that a sufficient amount of healing substance is maintained in the electrolyte during operation, allowing damage to the electrode boundary layer, caused by the initial substance added to the electrolyte to form the boundary layer, to be repaired.

[0056] Figure 3 schematically shows a diagram of a concentration K versus a number of charging cycles Z of the battery cell. Line A1 represents the concentration profile of the substance originally added to the electrolyte to form the boundary layer at an electrode. As can be seen in Figure 3, the concentration decreases exponentially with an increasing number of charging cycles. At point Z1, line A1 intersects a lower effective concentration K1 of the substance, thus initiating irreversible aging of the battery cell over time and with further cycles.

[0057] According to the invention, however, as shown by curve A2 in Figure 3, a release of the therapeutic substance from reservoir 5 into the electrolyte begins after a predetermined number of cycles Z0. This prevents the lower effective concentration K1 of the therapeutic substance from being undershot. The activation of reservoir 5 can be based on an internal pressure within battery cell 1 and / or a temperature of the battery cell.

[0058] According to the invention, reservoir 5 is designed such that the pressure and / or temperature thresholds inside battery cell 1 are reached approximately when the number of charge cycles Z0 of battery cell 1 has been reached. The invention thus exploits the fact that the pressure inside battery cell 1 tends to increase over time and with the number of charge cycles. Furthermore, during charging and / or discharging processes, the temperature also increases with the age of the battery cell due to an increase in the cell's internal resistance. This causes the battery cell itself to trigger the release of healing substance from reservoir 5, thereby automatically preventing irreversible damage to the boundary layer at an electrode, particularly at the anode, over the course of further charge cycles.

[0059] In the illustrated embodiment, the reservoir 5 is designed as a flat surface and is provided as a nonwoven fabric 52 impregnated with the healing substance. However, it should be noted that the reservoir 5 can also be designed as a flat capsule with a breakable capsule shell, as an impregnated sponge, as an impregnated fiber ball, or as a gel applied to a surface of the cell membrane. Furthermore, several identical or different reservoirs can be provided.

[0060] Figure 4 shows a battery cell 1 according to a second embodiment of the invention.

[0061] The reservoir 5 of the second embodiment is a capsule 53, which is arranged between the cell shell 4 and the cell stack 3. The capsule 53 can in turn be activated by pressure and / or temperature.

[0062] Figure 5 shows a cell shell 4 of a battery cell according to a third embodiment of the invention. As can be seen from Figure 4, the battery cell of the third embodiment has several reservoirs. In detail, the battery cell of the third embodiment has a first reservoir, which is a sponge 51 impregnated with an additive, a second reservoir, which is a nonwoven fabric 52 impregnated with an additive, and a third reservoir, which is a gel 54 containing a therapeutic substance. The nonwoven fabric 52 and the gel 54 are arranged between the base element 6 and the cell shell 4. The three reservoirs are preferably configured such that they are activated at different times during the battery cell's lifetime and release a therapeutic substance. This ensures that a sufficient amount of therapeutic substance is present in the electrolyte throughout the entire lifetime of the battery cell.Preferably, a constant level of therapeutic substance is maintained in the electrolyte. It is also possible for the various reservoirs to continuously release therapeutic substance into the electrolyte over time, with the amount released being either constant or variable over time.

[0063] Figures 6 and 7 schematically show a battery cell 1 according to a fourth embodiment, wherein the reservoir 5 is a capsule 53. Figure 6 shows the initial state with an intact capsule 53, and Figure 7 shows the state after pressure activation of the reservoir 5, such that the capsule has opened and the therapeutic substance has been released into the electrolyte, as indicated by arrows B. The release of the therapeutic substance reduces the volume of the capsule, which is indicated in Figure 7 by the reference numeral 53'.

[0064] As described in the preceding embodiments, the invention provides a battery cell 1 which exhibits a self-healing effect with respect to an interface layer at the electrodes, particularly at the anode. This ensures that an interface layer remains formed at one electrode throughout the entire service life of the battery cell 1. The healing substance is preferably the same substance as the starting substance added to the electrolyte to form the first interface layer when a voltage is first applied to the battery cell. By activating the reservoir 5 with pressure and / or temperature, the activation of the reservoir 5 can be controlled upon reaching a predetermined threshold, releasing the healing substance into the electrolyte, provided the reservoir 5 is appropriately designed. This may vary depending on the battery cell manufacturer.In particular, the integration of the reservoir 5 into a cell shell 4 is especially preferred, as this makes it possible to integrate the reservoir without modifications to other components of the battery cell.

Claims

Claims 1. Battery cell comprising: a housing (2), a cell stack (3) with an electrode, in particular an anode (31), a liquid electrolyte, wherein the cell stack (3) and the electrolyte are arranged in the housing (2), and a reservoir (5) with a healing substance which is configured to form an interface layer at the electrode, wherein the reservoir (5) is arranged in the housing (2), and wherein the reservoir (5) is configured to release the healing substance to the electrolyte in order to repair damage to the interface layer.

2. Battery cell according to claim 1, wherein the reservoir (5) is pressure-activated to release the healing substance to the electrolyte by applying pressure to the reservoir (5).

3. Battery cell according to claim 2, wherein the reservoir (5) is configured to increase the delivery quantity of the therapeutic substance with increasing pressure.

4. Battery cell according to one of the preceding claims, wherein the reservoir (5) is thermally activatable in order to release the healing substance to the electrolyte by applying a temperature to the reservoir (5).

5. Battery cell according to claim 4, wherein the reservoir (5) is configured to increase the amount of the therapeutic substance released with increasing temperature.

6. Battery cell according to claim 4 or 5, wherein the reservoir (5) in the battery cell is arranged at a position where a maximum temperature is reached during operation.

7. Battery cell according to one of the preceding claims, wherein the healing substance of the reservoirs (5) is the same substance as a substance contained in the electrolyte in the initial state of the electrolyte for the formation of the boundary layer at the electrode.

8. Battery cell according to one of the preceding claims, wherein the reservoir (5) is integrated into a component of the battery cell or is loosely arranged in the battery cell.

9. Battery cell according to one of the preceding claims, wherein the reservoir (5) is designed as a planar component.

10. Battery cell according to one of the preceding claims, wherein the healing substance is arranged in a capsule (53) with a destructible capsule housing.

11. Battery cell according to one of the preceding claims, wherein the healing substance is adsorbed in a sponge soaked with healing substance and / or in a nonwoven fabric soaked with healing substance (52) and / or in a fiber ball soaked with healing substance and / or onto a porous material, in particular activated carbon or silica gel.

12. Battery cell according to one of the preceding claims, wherein the healing substance is contained in a gel.

13. Battery cell according to one of the preceding claims, further comprising a polymer with absorbed therapeutic substance.

14. Battery cell according to one of the preceding claims, further comprising a cell shell (4) which is arranged between the housing (2) and the cell stack (3), wherein the reservoir (5) is arranged in a recess (40) in the cell shell (4) and / or wherein the reservoir is arranged on a side of the cell shell (4) facing the cell stack (3) and / or wherein the reservoir is arranged on a side of the cell shell (4) facing the housing (2).

15. Battery cell according to one of the preceding claims, further comprising a base element (6) on which the reservoir (5) is arranged.

16. Battery cell according to one of the preceding claims, comprising at least a first reservoir and a second reservoir which are configured to be activated at different times and / or which are configured to release equal or different amounts of therapeutic substance.

17. Battery cell according to claim 16, wherein a first activation mechanism of the first reservoir is different from a second activation mechanism of the second reservoir.

18. Battery cell according to one of the preceding claims, wherein the reservoir (5) can be activated from outside the battery cell to deliver therapeutic substance.

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